Can someone identify this thing

[xxjokerxx0415]

Does anyone know what in the world this is? It closes and opens. I feel like it opens with the current but sometimes feels like it opens when my clown fish are near it.

Also is that Cyanobacteria at on the sand bed?

Thank you in advance!!!

 

[Katrina71]

It actually looks like a piece of paper towel?

 

[xxjokerxx0415]

It actually looks like a piece of paper towel?

I think I would know what a piece of paper towel looks like lol